Move GetWindowsZOrder to IWindowingPlatform (#20633)

* Move GetWindowsZOrder to IWindowingPlatform

* Update API suppressions

api/Avalonia.nupkg.xml

@@ -1225,6 +1225,18 @@
     <Left>baseline/Avalonia/lib/net10.0/Avalonia.Controls.dll</Left>
     <Right>current/Avalonia/lib/net10.0/Avalonia.Controls.dll</Right>
   </Suppression>
+  <Suppression>
+    <DiagnosticId>CP0002</DiagnosticId>
+    <Target>M:Avalonia.Controls.Window.SortWindowsByZOrder(Avalonia.Controls.Window[])</Target>
+    <Left>baseline/Avalonia/lib/net10.0/Avalonia.Controls.dll</Left>
+    <Right>current/Avalonia/lib/net10.0/Avalonia.Controls.dll</Right>
+  </Suppression>
+  <Suppression>
+    <DiagnosticId>CP0002</DiagnosticId>
+    <Target>M:Avalonia.Platform.IWindowImpl.GetWindowsZOrder(System.Span{Avalonia.Controls.Window},System.Span{System.Int64})</Target>
+    <Left>baseline/Avalonia/lib/net10.0/Avalonia.Controls.dll</Left>
+    <Right>current/Avalonia/lib/net10.0/Avalonia.Controls.dll</Right>
+  </Suppression>
   <Suppression>
     <DiagnosticId>CP0002</DiagnosticId>
     <Target>M:Avalonia.Platform.Screen.#ctor(System.Double,Avalonia.PixelRect,Avalonia.PixelRect,System.Boolean)</Target>
@@ -2125,6 +2137,18 @@
     <Left>baseline/Avalonia/lib/net8.0/Avalonia.Controls.dll</Left>
     <Right>current/Avalonia/lib/net8.0/Avalonia.Controls.dll</Right>
   </Suppression>
+  <Suppression>
+    <DiagnosticId>CP0002</DiagnosticId>
+    <Target>M:Avalonia.Controls.Window.SortWindowsByZOrder(Avalonia.Controls.Window[])</Target>
+    <Left>baseline/Avalonia/lib/net8.0/Avalonia.Controls.dll</Left>
+    <Right>current/Avalonia/lib/net8.0/Avalonia.Controls.dll</Right>
+  </Suppression>
+  <Suppression>
+    <DiagnosticId>CP0002</DiagnosticId>
+    <Target>M:Avalonia.Platform.IWindowImpl.GetWindowsZOrder(System.Span{Avalonia.Controls.Window},System.Span{System.Int64})</Target>
+    <Left>baseline/Avalonia/lib/net8.0/Avalonia.Controls.dll</Left>
+    <Right>current/Avalonia/lib/net8.0/Avalonia.Controls.dll</Right>
+  </Suppression>
   <Suppression>
     <DiagnosticId>CP0002</DiagnosticId>
     <Target>M:Avalonia.Platform.Screen.#ctor(System.Double,Avalonia.PixelRect,Avalonia.PixelRect,System.Boolean)</Target>
@@ -2377,6 +2401,12 @@
     <Left>baseline/Avalonia/lib/net10.0/Avalonia.Base.dll</Left>
     <Right>current/Avalonia/lib/net10.0/Avalonia.Base.dll</Right>
   </Suppression>
+  <Suppression>
+    <DiagnosticId>CP0006</DiagnosticId>
+    <Target>M:Avalonia.Platform.IWindowingPlatform.GetWindowsZOrder(System.ReadOnlySpan{Avalonia.Platform.IWindowImpl},System.Span{System.Int64})</Target>
+    <Left>baseline/Avalonia/lib/net10.0/Avalonia.Controls.dll</Left>
+    <Right>current/Avalonia/lib/net10.0/Avalonia.Controls.dll</Right>
+  </Suppression>
   <Suppression>
     <DiagnosticId>CP0006</DiagnosticId>
     <Target>M:Avalonia.OpenGL.Surfaces.IGlPlatformSurfaceRenderTarget.BeginDraw(System.Nullable{Avalonia.PixelSize})</Target>
@@ -2575,6 +2605,12 @@
     <Left>baseline/Avalonia/lib/net8.0/Avalonia.Base.dll</Left>
     <Right>current/Avalonia/lib/net8.0/Avalonia.Base.dll</Right>
   </Suppression>
+  <Suppression>
+    <DiagnosticId>CP0006</DiagnosticId>
+    <Target>M:Avalonia.Platform.IWindowingPlatform.GetWindowsZOrder(System.ReadOnlySpan{Avalonia.Platform.IWindowImpl},System.Span{System.Int64})</Target>
+    <Left>baseline/Avalonia/lib/net8.0/Avalonia.Controls.dll</Left>
+    <Right>current/Avalonia/lib/net8.0/Avalonia.Controls.dll</Right>
+  </Suppression>
   <Suppression>
     <DiagnosticId>CP0006</DiagnosticId>
     <Target>M:Avalonia.OpenGL.IGlExternalSemaphore.SignalTimelineSemaphore(Avalonia.OpenGL.IGlExternalImageTexture,System.UInt64)</Target>

src/Android/Avalonia.Android/Stubs.cs

@@ -12,6 +12,8 @@ namespace Avalonia.Android
         public IWindowImpl CreateEmbeddableWindow() => throw new NotSupportedException();
 
         public ITrayIconImpl? CreateTrayIcon() => null;
+
+        public void GetWindowsZOrder(ReadOnlySpan<IWindowImpl> windows, Span<long> zOrder) => throw new NotSupportedException();
     }
 
     internal class PlatformIconLoaderStub : IPlatformIconLoader

src/Avalonia.Controls/Platform/IWindowImpl.cs

@@ -153,14 +153,5 @@ namespace Avalonia.Platform
         /// </summary>
         /// <param name="titleBarHeight">-1 for platform default, otherwise the height in DIPs.</param>
         void SetExtendClientAreaTitleBarHeightHint(double titleBarHeight);
-
-        /// <summary>
-        /// Fills zOrder with numbers that represent the relative order of the windows in the z-order.
-        /// The topmost window should have the highest number.
-        /// Both the windows and zOrder lists are expected to be the same length.
-        /// </summary>
-        /// <param name="windows">A span of windows to get their z-order</param>
-        /// <param name="zOrder">Span to be filled with associated window z-order</param>
-        void GetWindowsZOrder(Span<Window> windows, Span<long> zOrder);
     }
 }

src/Avalonia.Controls/Platform/IWindowingPlatform.cs

@@ -1,3 +1,4 @@
+using System;
 using Avalonia.Metadata;
 
 namespace Avalonia.Platform
@@ -12,5 +13,14 @@ namespace Avalonia.Platform
         IWindowImpl CreateEmbeddableWindow();
 
         ITrayIconImpl? CreateTrayIcon();
+
+        /// <summary>
+        /// Fills a span with numbers that represent the relative order of the windows in the z-order.
+        /// The topmost window should have the highest number.
+        /// Both the <paramref name="windows"/> and <paramref name="zOrder"/> lists are expected to be the same length.
+        /// </summary>
+        /// <param name="windows">A span of windows to get their z-order.</param>
+        /// <param name="zOrder">The span to be filled with the associated window z-order.</param>
+        void GetWindowsZOrder(ReadOnlySpan<IWindowImpl> windows, Span<long> zOrder);
     }
 }

src/Avalonia.Controls/Window.cs

@@ -903,24 +903,25 @@ namespace Avalonia.Controls
         /// <summary>
         /// Sorts the windows ascending by their Z order - the topmost window will be the last in the list.
         /// </summary>
-        /// <param name="windows"></param>
-        public static void SortWindowsByZOrder(Window[] windows)
+        /// <param name="windows">The windows to sort.</param>
+        public static void SortWindowsByZOrder(Span<Window> windows)
         {
-            if (windows.Length == 0)
+            if (windows.Length <= 1)
                 return;
 
-            if (windows[0].PlatformImpl is not { } platformImpl)
-                throw new InvalidOperationException("Window.PlatformImpl is null");
-
-#if NET5_0_OR_GREATER
-            Span<long> zOrder = stackalloc long[windows.Length];
-            platformImpl.GetWindowsZOrder(windows, zOrder);
-            zOrder.Sort(windows.AsSpan());
-#else
-            long[] zOrder = new long[windows.Length];
-            platformImpl.GetWindowsZOrder(windows, zOrder);
-            Array.Sort(zOrder, windows);
-#endif
+            var platform = AvaloniaLocator.Current.GetRequiredService<IWindowingPlatform>();
+
+            var windowImpls = new IWindowImpl[windows.Length];
+            for (var i = 0; i < windows.Length; ++i)
+            {
+                windowImpls[i] = windows[i].PlatformImpl ??
+                                 throw new ArgumentException($"Invalid window at index {i}", nameof(windows));
+            }
+
+            const int stackAllocThreshold = 128;
+            var zOrder = windows.Length > stackAllocThreshold ? new long[windows.Length] : stackalloc long[windows.Length];
+            platform.GetWindowsZOrder(windowImpls, zOrder);
+            zOrder.Sort(windows);
         }
 
         private void UpdateEnabled()

src/Avalonia.DesignerSupport/Remote/PreviewerWindowImpl.cs

@@ -170,7 +170,5 @@ namespace Avalonia.DesignerSupport.Remote
         public void SetExtendClientAreaTitleBarHeightHint(double titleBarHeight)
         {            
         }
-
-        public void GetWindowsZOrder(Span<Window> windows, Span<long> zOrder) => throw new NotSupportedException();
     }
 }

src/Avalonia.DesignerSupport/Remote/PreviewerWindowingPlatform.cs

@@ -44,6 +44,9 @@ namespace Avalonia.DesignerSupport.Remote
             return s_lastWindow;
         }
 
+        public void GetWindowsZOrder(ReadOnlySpan<IWindowImpl> windows, Span<long> zOrder)
+            => zOrder.Clear();
+
         public static void Initialize(IAvaloniaRemoteTransportConnection transport)
         {
             s_transport = transport;

src/Avalonia.DesignerSupport/Remote/Stubs.cs

@@ -182,8 +182,6 @@ namespace Avalonia.DesignerSupport.Remote
         {
         }
 
-        public void GetWindowsZOrder(Span<Window> windows, Span<long> zOrder) => throw new NotSupportedException();
-
         public IPopupPositioner? PopupPositioner { get; }
 
         public Action? GotInputWhenDisabled { get; set; }

src/Avalonia.Native/AvaloniaNativePlatform.cs

@@ -2,6 +2,7 @@
 using System.Collections.Generic;
 using System.Runtime.InteropServices;
 using Avalonia.Compatibility;
+using Avalonia.Controls;
 using Avalonia.Controls.ApplicationLifetimes;
 using Avalonia.Controls.Platform;
 using Avalonia.Input;
@@ -210,5 +211,13 @@ namespace Avalonia.Native
         {
             return new EmbeddableTopLevelImpl(_factory);
         }
+
+        public void GetWindowsZOrder(ReadOnlySpan<IWindowImpl> windows, Span<long> zOrder)
+        {
+            for (var i = 0; i < windows.Length; i++)
+            {
+                zOrder[i] = (windows[i] as WindowImpl)?.ZOrder?.ToInt64() ?? 0;
+            }
+        }
     }
 }

src/Avalonia.Native/WindowImpl.cs

@@ -271,13 +271,5 @@ namespace Avalonia.Native
             
             return base.TryGetFeature(featureType);
         }
-
-        public void GetWindowsZOrder(Span<Window> windows, Span<long> zOrder)
-        {
-            for (int i = 0; i < windows.Length; i++)
-            {
-                zOrder[i] = (windows[i].PlatformImpl as WindowImpl)?.ZOrder?.ToInt64() ?? 0;
-            }
-        }
     }
 }

src/Avalonia.X11/X11Platform.cs

@@ -230,6 +230,83 @@ namespace Avalonia.X11
 
             throw new InvalidOperationException($"{nameof(X11PlatformOptions)}.{nameof(X11PlatformOptions.RenderingMode)} has a value of \"{string.Join(", ", opts.RenderingMode)}\", but no options were applied.");
         }
+
+        public void GetWindowsZOrder(ReadOnlySpan<IWindowImpl> windows, Span<long> outputZOrder)
+        {
+            // a mapping of parent windows to their children, sorted by z-order (bottom to top)
+            var windowsChildren = new Dictionary<IntPtr, List<IntPtr>>();
+
+            var indexInWindowsSpan = new Dictionary<IntPtr, int>();
+            for (var i = 0; i < windows.Length; i++)
+                if (windows[i] is X11Window { Handle: { } handle })
+                    indexInWindowsSpan[handle.Handle] = i;
+
+            foreach (var window in windows)
+            {
+                if (window is not X11Window x11Window)
+                    continue;
+
+                var node = x11Window.Handle.Handle;
+                while (node != IntPtr.Zero)
+                {
+                    if (windowsChildren.ContainsKey(node))
+                    {
+                        break;
+                    }
+
+                    if (XQueryTree(Info.Display, node, out _, out var parent,
+                            out var childrenPtr, out var childrenCount) == 0)
+                    {
+                        break;
+                    }
+
+                    if (childrenPtr != IntPtr.Zero)
+                    {
+                        unsafe
+                        {
+                            var children = (IntPtr*)childrenPtr;
+                            windowsChildren[node] = new List<IntPtr>(childrenCount);
+                            for (var i = 0; i < childrenCount; i++)
+                            {
+                                windowsChildren[node].Add(children[i]);
+                            }
+
+                            XFree(childrenPtr);
+                        }
+                    }
+
+                    node = parent;
+                }
+            }
+
+            var stack = new Stack<IntPtr>();
+            var zOrder = 0;
+            stack.Push(Info.RootWindow);
+
+            while (stack.Count > 0)
+            {
+                var currentWindow = stack.Pop();
+
+                if (!windowsChildren.TryGetValue(currentWindow, out var children))
+                {
+                    continue;
+                }
+
+                if (indexInWindowsSpan.TryGetValue(currentWindow, out var index))
+                {
+                    outputZOrder[index] = zOrder;
+                }
+
+                zOrder++;
+
+                // Children are returned bottom to top, so we need to push them in reverse order
+                // In order to traverse bottom children first
+                for (int i = children.Count - 1; i >= 0; i--)
+                {
+                    stack.Push(children[i]);
+                }
+            }
+        }
     }
 }
 

src/Avalonia.X11/X11Window.cs

@@ -1557,80 +1557,6 @@ namespace Avalonia.X11
 
         }
 
-        /// <inheritdoc/>
-        public void GetWindowsZOrder(Span<Window> windows, Span<long> outputZOrder)
-        {
-            // a mapping of parent windows to their children, sorted by z-order (bottom to top)
-            var windowsChildren = new Dictionary<IntPtr, List<IntPtr>>();
-
-            var indexInWindowsSpan = new Dictionary<IntPtr, int>();
-            for (var i = 0; i < windows.Length; i++)
-                if (windows[i].PlatformImpl is { Handle: { } handle })
-                    indexInWindowsSpan[handle.Handle] = i;
-
-            foreach (var window in windows)
-            {
-                if (window.PlatformImpl is not X11Window x11Window)
-                    continue;
-
-                var node = x11Window.Handle.Handle;
-                while (node != IntPtr.Zero)
-                {
-                    if (windowsChildren.ContainsKey(node))
-                    {
-                        break;
-                    }
-
-                    if (XQueryTree(_x11.Display, node, out _, out var parent,
-                            out var childrenPtr, out var childrenCount) == 0)
-                    {
-                        break;
-                    }
-
-                    if (childrenPtr != IntPtr.Zero)
-                    {
-                        var children = (IntPtr*)childrenPtr;
-                        windowsChildren[node] = new List<IntPtr>(childrenCount);
-                        for (var i = 0; i < childrenCount; i++)
-                        {
-                            windowsChildren[node].Add(children[i]);
-                        }
-                        XFree(childrenPtr);
-                    }
-
-                    node = parent;
-                }
-            }
-
-            var stack = new Stack<IntPtr>();
-            var zOrder = 0;
-            stack.Push(_x11.RootWindow);
-
-            while (stack.Count > 0)
-            {
-                var currentWindow = stack.Pop();
-
-                if (!windowsChildren.TryGetValue(currentWindow, out var children))
-                {
-                    continue;
-                }
-
-                if (indexInWindowsSpan.TryGetValue(currentWindow, out var index))
-                {
-                    outputZOrder[index] = zOrder;
-                }
-
-                zOrder++;
-
-                // Children are returned bottom to top, so we need to push them in reverse order
-                // In order to traverse bottom children first
-                for (int i = children.Count - 1; i >= 0; i--)
-                {
-                    stack.Push(children[i]);
-                }
-            }
-        }
-
         public void TakeFocus()
         {
             // TODO: Not yet implemented: need to check if this is required on X11 or not.

src/Browser/Avalonia.Browser/WindowingPlatform.cs

@@ -74,6 +74,9 @@ internal class BrowserWindowingPlatform : IWindowingPlatform
         return null;
     }
 
+    public void GetWindowsZOrder(ReadOnlySpan<IWindowImpl> windows, Span<long> zOrder)
+        => throw new NotSupportedException();
+
     public static KeyboardDevice Keyboard => s_keyboard ??
         throw new InvalidOperationException("BrowserWindowingPlatform not registered.");
 

src/Headless/Avalonia.Headless/AvaloniaHeadlessPlatform.cs

@@ -63,6 +63,14 @@ namespace Avalonia.Headless
             public IWindowImpl CreateEmbeddableWindow() => throw new PlatformNotSupportedException();
 
             public ITrayIconImpl? CreateTrayIcon() => null;
+
+            public void GetWindowsZOrder(ReadOnlySpan<IWindowImpl> windows, Span<long> zOrder)
+            {
+                for (var i = 0; i < windows.Length; ++i)
+                {
+                    zOrder[i] = (windows[i] as HeadlessWindowImpl)?.ZOrder ?? 0;
+                }
+            }
         }
         
         internal static void Initialize(AvaloniaHeadlessPlatformOptions opts)

src/Headless/Avalonia.Headless/HeadlessWindowImpl.cs

@@ -25,7 +25,6 @@ namespace Avalonia.Headless
         private WriteableBitmap? _lastRenderedFrame;
         private readonly object _sync = new object();
         private readonly PixelFormat _frameBufferFormat;
-        private int _zOrder;
         public bool IsPopup { get; }
 
         public HeadlessWindowImpl(bool isPopup, PixelFormat frameBufferFormat)
@@ -59,6 +58,8 @@ namespace Avalonia.Headless
 
         public Compositor Compositor => AvaloniaHeadlessPlatform.Compositor!;
 
+        public int ZOrder { get; private set; }
+
         public void SetInputRoot(IInputRoot inputRoot)
         {
             InputRoot = inputRoot;
@@ -82,7 +83,7 @@ namespace Avalonia.Headless
         {
             if (activate)
             {
-                _zOrder = _nextGlobalZOrder++;
+                ZOrder = _nextGlobalZOrder++;
                 Dispatcher.UIThread.Post(() => Activated?.Invoke(), DispatcherPriority.Input);
             }
         }
@@ -96,7 +97,7 @@ namespace Avalonia.Headless
         public Action<PixelPoint>? PositionChanged { get; set; }
         public void Activate()
         {
-            _zOrder = _nextGlobalZOrder++;
+            ZOrder = _nextGlobalZOrder++;
             Dispatcher.UIThread.Post(() => Activated?.Invoke(), DispatcherPriority.Input);
         }
 
@@ -430,15 +431,6 @@ namespace Avalonia.Headless
             
         }
 
-        public void GetWindowsZOrder(Span<Window> windows, Span<long> zOrder)
-        {
-            for (int i = 0; i < windows.Length; ++i)
-            {
-                if (windows[i].PlatformImpl is HeadlessWindowImpl headlessWindowImpl)
-                    zOrder[i] = headlessWindowImpl._zOrder;
-            }
-        }
-
         public void TakeFocus() 
         {
         }

src/Windows/Avalonia.Win32/Win32Platform.cs

@@ -323,5 +323,33 @@ namespace Avalonia.Win32
             if (dpiAwareness != Win32DpiAwareness.Unaware)
                 SetProcessDPIAware();
         }
+
+        public void GetWindowsZOrder(ReadOnlySpan<IWindowImpl> windows, Span<long> zOrder)
+        {
+            var handlesToIndex = new Dictionary<IntPtr, int>(windows.Length);
+            var outputArray = new long[windows.Length];
+
+            for (int i = 0; i < windows.Length; i++)
+            {
+                if (windows[i] is WindowImpl platformImpl)
+                    handlesToIndex.Add(platformImpl.Handle.Handle, i);
+            }
+
+            long nextZOrder = 0;
+            bool EnumWindowsProc(IntPtr hWnd, IntPtr lParam)
+            {
+                if (handlesToIndex.TryGetValue(hWnd, out var index))
+                {
+                    // We negate the z-order so that the topmost window has the highest number.
+                    outputArray[index] = -nextZOrder;
+                    nextZOrder++;
+                }
+                return nextZOrder < outputArray.Length;
+            }
+
+            EnumChildWindows(IntPtr.Zero, EnumWindowsProc, IntPtr.Zero);
+
+            outputArray.CopyTo(zOrder);
+        }
     }
 }

src/Windows/Avalonia.Win32/WindowImpl.cs

@@ -1613,38 +1613,6 @@ namespace Avalonia.Win32
             ExtendClientArea();
         }
 
-        /// <inheritdoc/>
-        public void GetWindowsZOrder(Span<Window> windows, Span<long> zOrder)
-        {
-            var handlesToIndex = new Dictionary<IntPtr, int>(windows.Length);
-            var outputArray = new long[windows.Length];
-
-            for (int i = 0; i < windows.Length; i++)
-            {
-                if (windows[i].PlatformImpl is WindowImpl platformImpl)
-                    handlesToIndex.Add(platformImpl.Handle.Handle, i);
-            }
-
-            long nextZOrder = 0;
-            bool EnumWindowsProc(IntPtr hWnd, IntPtr lParam)
-            {
-                if (handlesToIndex.TryGetValue(hWnd, out var index))
-                {
-                    // We negate the z-order so that the topmost window has the highest number.
-                    outputArray[index] = -nextZOrder;
-                    nextZOrder++;
-                }
-                return nextZOrder < outputArray.Length;
-            }
-
-            EnumChildWindows(IntPtr.Zero, EnumWindowsProc, IntPtr.Zero);
-
-            for (int i = 0; i < windows.Length; i++)
-            {
-                zOrder[i] = outputArray[i];
-            }
-        }
-
         /// <inheritdoc/>
         public bool IsClientAreaExtendedToDecorations => _isClientAreaExtended;
 

src/iOS/Avalonia.iOS/Stubs.cs

@@ -25,6 +25,9 @@ namespace Avalonia.iOS
         public IWindowImpl CreateEmbeddableWindow() => throw new NotSupportedException();
 
         public ITrayIconImpl? CreateTrayIcon() => null;
+
+        public void GetWindowsZOrder(ReadOnlySpan<IWindowImpl> windows, Span<long> zOrder)
+            => throw new NotSupportedException();
     }
     
     internal class PlatformIconLoaderStub : IPlatformIconLoader

tests/Avalonia.UnitTests/MockWindowingPlatform.cs

@@ -162,5 +162,8 @@ namespace Avalonia.UnitTests
         {
             return null;
         }
+
+        public void GetWindowsZOrder(ReadOnlySpan<IWindowImpl> windows, Span<long> zOrder)
+            => zOrder.Clear();
     }
 }